It is known that, for the production of oil, it is also possible to use oil deposits in which the oil needs to be separated from the sand in a separation process. In deposits in which the oil sands are not accessible using open-pit mining, however, production of the oil may be performed by heating the oil sands. As a result, the viscosity of the bound oil is reduced such that the oil may be pumped away in a conventional manner. In known methods, heated vapor, heated air, or similar hot gases are used for heating the oil sands. This is associated with the disadvantage that it is necessary to provide the possibility, in a very complex manner, of transporting the gases into the desired position in the ground, namely to the deposit location of the oil sands. Furthermore, owing to sometimes very deep and extensive deposits, a high degree of complexity in respect of the pressure loss occurring during introduction of the gases/vapors needs to be considered.
It is furthermore known that an induction cable is used to generate an induced eddy current in the surrounding ground for heating the ground. Alternating current with a frequency range of from 10 kHz to 200 kHz may be applied to such an induction cable, and such an induction cable is laid as a conductor loop in the ground of a reservoir.
In order to achieve the desired induced eddy currents in the ground, a corresponding alternating current is applied to the conductor loop. Owing to the long length of such a conductor loop that may be up to several kilometers, however, there is the problem that relatively high voltage drops are produced by the voltages induced in the surrounding ground. These high voltage drops result in immense costs and complexities in terms of the device for operating such a conductor loop.
WO 2009/027305 A2 discloses, in principle, a solution to such a problem. The document describes that individual filaments form a conductor with a distributed capacitance. In other words, a multiplicity of capacitors is distributed substantially constantly over the course of the conductor loop, with the result that compensation of the inductive voltage drop may be produced by these capacitors.
One disadvantage with the above-described solution is that the distributed capacitor arrangement represents a restriction in terms of the mechanical properties of the conductor loop itself. The conductor loop needs to be introduced into the ground, for example, through a bore hole. Furthermore, the conductor loop does not necessarily run along a straight path, but may also have bends and curvatures. Correspondingly, care needs to be taken when introducing and operating such a conductor loop to provide that the line elements or all of the component parts of the conductor loop withstand corresponding tensile loading or corresponding bending loading. This provides that known conductor loops with distributed capacitances cannot be used in all use sectors. Furthermore, the use possibilities for a wide variety of materials for the dielectric materials of the individual capacitors are restricted since the materials likewise need to withstand the corresponding bending stresses and tensile stresses. Furthermore, this results in larger cable thicknesses or poorer compensation performances.